Oscillation generator



July 26, 1932. ROSE 1,869,171

OSCILLATION GENERATOR Filed June 10. 1930 AMPL lF/EI? IN VENTOR Ci/TERDSE i at ." frequency of vibration.

Patented July 26, 1932 UNITED STATES CHARLES IE. P. ROSE, OI NEW YORK, N. Y.,

ess rpa sq. t k roams, INCORPORATED, on NEW YORKgNF Y., A. con-ronnrsto n oi-nnw Y'o'itK OSCILLATION assurances l Application filed .Tune 10,

This invention relates to oscillation generators and particularly to those whose'frequency is controlled by a mechanical vibrating element such as a piezo electric crystal. Such generators are in wide use and are particularly adapted to systems in which it is necessary to maintain the frequency constant within narrow limits as, for example, in high frequency radio signaling systems.

In connection with such a system, a spare crystal may be provided which has been designed to vibrate at the same frequency as the working crystal, and means may be provided to switch the spare crystal into operation when desired, as in the case of a failure of the working crystal. The frequency of vibration of a crystal is a function of its temperature, and the temperature of the crystal in turn is a function of the amplitude of its vibrations and of the impedance of the cir cuit into which the crystal is vibrating.

If a spare crystal which has been idle is switched into an oscillator circuit and caused to vibrate, there will be a change in its temperature and a corresponding change in its This not only changes the frequency of the oscillator, but necessitates a readjustment of the circuit to maintain oscillation at the changed frequency.

If means are provided to maintain the spare crystal in vibration, and it is then switched into the oscillator circuit, there will be a change in its frequency of vibration due to the difference in the impedance of the load into which the crystal is vibrating, with at,

least qualitatively, the same effect as before.

It is the object of this invention to provide means for switching the spare crystal into an oscillator circuit without affecting the operation of the circuit. r

This may be accomplished by providing a separate oscillating circuit for the spare crystal, and a dummy load into which it may vibrate which has the same characteristics as the load into which the working crystal is vibrating.

Additional features of the invention and characteristics of its operation will appear from the following detailed description when 199a see-a1 mam-25s. readwith the; Q idrawinlg r -he single. figure of which illustrates a preferred embodiment of theinvention;

. The figu'reoff the drawing i'sr-a dream be a the circuits of two crystal controlled osjcilla-tors and, an amplifier which may.- boas-'1 sociated with a radio transmitting or receiving system or other suitable apparatus; Two

mechanical vibrating elements Land 2, haying thesame frequency characteristics,- which maybe piezo-electriccrystals, and are preftemperature, are. connected acrossresistanoes V ,3 ands: respectively in the input cirouitsof er'ably maintained at the same constant A com-monbattery9 supplies plat-e current for the two oscillators. Separate output circuits include respectively tuned circuits 10 from the plate of e'aehtube is connected to a i and 11 and milliammeters 12 and 13; A lead throw switch .14. When the switch isjclosed ingthe position to the right, the oscillatof of tube 5 is connected to the amplifier shown in block, and the oscillator of tube 6 is connected to a variable condenser 15. When the switch 14 is thrown to the left, the oscillator of tube 5isconn-ected to the condenser 15, and

amplifier. The condenser 15 may.be adjusted by varying its capacity until it simulates the impedance of the amplifier.

' Assuming the oscillator'of tube 5 is being used as the working oscillator, the switch will I the oscillator of tube 6 is connected'to the then be closed to the right. Both the oscillators are vibrating however, and they are operating into equivalentloads; If. it is desired to switch crystals, as in the case of a failure of the oscillator of tube 5 due to a breakdown of the crystal 1 or for any other reason, the

switch 14: is thrown to the left, and the ap paratus continues to operate exactly as be fore except that the oscillator of tube 6, controlled by crystal 2, now suppliesthe oscilla-,

Crystal controlled oscillators are particu-" larly advantageous at high frequencies, due to thedifiiculty in maintaining oscillations constant at such frequencies by any other means. When used at high frequencies a balanced amplifier should be used to prevent reaction in the amplifier, or from the amplifier to the oscillator, which would tend'to cause a change in the crystal frequency.

What is claimed is: 1. Anoscillation producing system com prising a crystal controlled oscillator, a Work circuit connected thereto, a spare crystal controlled oscillator, means to substitute said spare oscillator for saidfirstmentioned oscillator, and means associated with said spare oscillator prior to the substitution to sub ect the spare oscillator to the same electrical con I ditions as said first mentioned oscillator whereby upon substitution of said spare 0scillator the amplitude of the oscillations sup plied to said Work circuit will not undergo change.

2. A- mechanically controlled oscillation ygenerator a second mechanically controlled oscillation generator, an electrical circuit connected to the output of said oscillation generator, a dummy load circuit of the same imr pedance as said electricalcircuit connected to the output of said second oscillation generator, and switching means for simultaneously transposing said connections.

3; A crystal controlled oscillation generator, a spare crystal therefor, means for maintaining said spare crystal in vibration, and

means for switching said spare crystal into the circuit of said generator Without affecting the amplitude of vibration of the crystal.

In Witness whereof, I hereunto subscribe my name this 10th day of June, 1930'.

CHARLES F. P. ROSE. 

